Light-emitting diode (LED) cutting technology is evolving from diamond tool cutting to laser cutting. In laser cutting, the wavelength is generally 355 nm or 266 nm, sufficient to scribe sapphire substrates and various film layers, such as GaN layers, Bragg reflective layers and metal layers.
Referring to FIG. 1, invisible laser cutting for LED has emerged and developed rapidly in recent years. It can penetrate the sapphire substrate 10 by forming explosion points 11 that are full of energy inside the sapphire substrate 10. With explosion of the explosion points 11, the sapphire substrate is thereby cut apart. Compared with ordinary laser cutting or diamond cutting, the invisible laser cutting reduces the laser burning area at wafer side or the injury area on wafer surface, leading to less light loss of wafer; however, as explosion points 11 form inside the substrate 10, materials at the region of explosion points 11 after laser burning would adhere to the side wall of the explosion points 11, thus blocking light from emitting and influencing external quantum efficiency of the LED.